Our research interest is in the biochemical and electrophysiological correlates of learning. Specifically, we are studying the process of habituation in the contractile protozoan, Stentor coeruleus. Previously performed work shows this process is similar to metazoan habituation and that it is correlated with a progressive decrement in receptor amplitude. Recent studies indicate that the reduction in receptor potential amplitude is not due to a change in ionic activities but rather results from a change in the membrane transduction mechanism. We have also observed that this transduction mechanism contains a curariform binding site. The studies proposed in this application are designed to elucidate the function of this binding site and to characterize the binding of radioactive curare and bungarotoxin. Subsequent to this characterization of the binding site it is proposed to use the binding of these radioactive compounds to stentor to study what changes take place in the membrane during habituation. BIBLIOGRAPHIC REFERENCE: Wood, D.C. Protozoa as models of stimulus transduction. In Aneural Organisms: Their Significance for Neurobiology, E. Eisenstein (ed.), Plenum Press: New York (1975).